Slotted core lifter apparatus



United States Patent lnventor Barry W. Brown North Bay, Ontario, CanadaAppl. No. 829,279 Filed June 2, 1969 Patented Nov. 17, 1970 Assignee E.J. Longyear Company Minneapolis, Minnesota a corporation of DelawareSLOTTED CORE LIFTER APPARATUS 12 Claims, 4 Drawing Figs.

US. Cl 175/251, 175/255 Int. Cl E2lb 25/00 Field of Search 175/249, 251,255, 244

Primary Examiner-David H. Brown Attorney-Bugger, Peterson, Johnson andWestman ABSTRACT: Core barrel apparatus for drilling core from an earthformation, for receiving core as it is drilled, breaking the drilledcore from the earth formation, and retaining the core as the core isretracted through the drill hole, said apparatus including a core lifterhaving a plurality of axially elongated circumferentially spaced slots,some of the slots opening to the top edge and others the bottom edge ofthe core lifter.

Pa tenta Nov. 17, 1970 FIEIQ [FYI I Arron/5r:

SLOTTED CORE LIFTER APPARATUS BACKGROUND OF THE INVENTION This inventionrelates to core drilling apparatus that has a core lifter mounted in acore lifter case for limited relative axial movement for breaking a corefrom an earth formation and retaining. the core as the core is retractedthrough a drill hole.

In core drilling art, it is common to provide a drill stem having a corebarrel outer tube at the inner axial end thereof with a core barrelinner tube within the outer tube for receiving the core as it isproduced by the drilling operation. For purposes of breaking loose thedrilled core from the earth formation, when the core barrel inner tubeis filled, it is conventional to provide a core lifter case on the inneraxial end of the core barrel inner tube, and a core lifter in the formofa small axially split ring having an exterior tapered or conicalsurface which bears upon a corresponding surface of the core lifter caseand an interior toothed surface for gripping the core. Theaforementioned type core lifter apparatus has been used both with wireline core barrel inner tube assemblies which are retractable independentof and through the drill stem, and core barrel inner tubes that aremounted in the drill stem in a manner such as disclosed in U.S. Pat. No.2,522,399 in which the entire drill stem has to be removed from the holein the earth formation in order to retrieve the core. In order toretrieve the core, whether it be with wire line type equipment or thetype in which the entire drill stem has to be retrieved, usually asubstantial pulling force has to be exerted on the drill stem and thusto the core lifter apparatus in order to initially break the core afterit has been drilled from the earth formation. After the core has beenbroken, thence the core barrel inner tube is retracted in order toretrieve the core.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS The inventionis illustrated with reference to the drawings wherein:

FIG. 1 is a fragmentary longitudinal cross-sectional view of the inneraxial end of the drill stem and core barrel inner tube, together withcore lifter apparatus attached to said inner tube;

FIG. 2 is a transverse cross-sectional view of the core lifter and corelifter case, said view generally being taken along the line and in thedirection of the arrows 2-2 of FIG. 1'.

FIG. 3 is a perspective view of the core lifter of this invention; and

FIG. 4 is a view of the core lifter that is generally taken along theline and in the direction of the arrows 4-4 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT For purposes of facilitating thedescription of the invention, the term inner" refers to the portion ofthe drillstem or of the assembly, or an element being described which inits position for use in the drill stem is located closer to core bit onthe drill stem than any other portion of the apparatus being described,except where the term clearly refers to a transverse circumference,direction or diameter of the drill stem or other apparatus beingdescribed. The term outer" refers to that portion of the drill stem, orof the assembly, or element being described which in its position foruse" in the drill stem is located closer to the mouth of the drill holethan any other portion of the apparatus being described, except wherethe term clearly refers to a transverse circumference, direction ordiameter of the apparatus being described.

Referring now to FIG. I. there is illustrated the inner end portion ofadrill stem II, the portion illustrated constituting a portion of what isfrequently referred to as the core barrel outer tube. To the inner endof the drill stem there is threadedly connected a rotary core bit 12that is rotated by the drill stem to drill a core. The core bit has acentral aperture 13 that is provided for boring the core in an earthformation 14. Located within the drill stem in a position to receivecore as it is being drilled is a core barrel inner tube assembly havinga core barrel inner tube 17, a core lifter case generally designated 18being threadedly connected to the inner axial end of the inner tube anda core lifter 19 slidably retained in the core lifter case. It is notedthat the only portion of the core barrel inner tube assembly illustratedis the inner axial end of the inner tube the core lifter case and thecore lifter: however. it is to be understood the core barrel inner tubeassembly can be of a wire line type that is retractable through a drillstem, the core barrel inner tube assembly disclosed in U.S. Pat. No.2,829,868 being one example of such type; or a core barrel inner tubeassembly that is not retractable independent of the drill stem, U.S.Pat. No. 2,522,399 being one example of this type.

The outer end portion 21 of the core lifter case 18 has internal threads18c that form a matching fit with the external threads of the corereceiving tube. The case 18 has an internal annular groove o'r recess 20that is located a short distance axially inwardly of the threads 18c andhas an outer transverse annular edge 20;: that is located in a planenormal to the central axis L-L of the-core barrel inner tube interiorand exterior surfaces, and the tapered surface 23, the beveled surface24, the generally cylindrically exterior surface 18a and the conical ortapered surface 18b of the core lifter case. The recess 20 has an axialsurface 200 that is centered with reference to the axis L4. and agenerally annular edge 20b.

The core lifter case has an axially elongated, gradually tapered axialinner surface 23 that at its outer axial end joins with the inner radialedge of the surface 20b and at its opposite end joins with the beveledsurface 24. The taper is such that the diametric dimension adjacentsurface 24 is less than that at any axial position more closely adjacentgroove 20.

The core lifter case at its inner axial end has the beveled surface 24that is of progressively increasing diameters in an axial directiontoward the core bit aperture and a transverse outer beveled surface 18bof an angle of taper to form a mating fit with the inclined shoulder 12aof the core bit. Advantageously during the drilling operation, surface18 b is spaced relative to surface 12a such as illustrated in FIG. 1;however, it is to be understood that insofar as the invention isconcerned, these surfaces may be in abutting relationship at the timecore is being drilled and appropriate fluid channels provided forconducting fluid from the annular space between the drill stem and thecore lifter case to aperture I3 or to the core bit face 13b.

The core lifter case mounts for axial movement relative thereto, thecore lifter 19 for grippingly holding and breaking a core as the drillstem is retracted. That is, the core lifter comprises a resilient splitsteel ring having a smooth, cylindrical, transverse inner surface 19athat at the outer end ter minates at the outer edge 19b. Surface l9aextends substantially the entire axial length of the case, surface atits axial inner edge. intersecting the smooth transverse inner conicalsurface 190 which at its inner end terminates at the inner edge 19d ofthe core lifter. The central axis L-L of the core lifter,

the inner tube and the core lifter case is equally radially spaced fromsaid inner surface 19a throughout the axial length of said inner surfacewhile the inner conical surface 190 is tapered to in an inner axialdirection be progressively further axially spaced from said axis. Thecore lifter 19 also has a smooth, transverse outer axial conical surfacel9e that is tapered to mate with the core lifter case surface 23 andthat extends axially from edge 19b to edge 19d. In a plane containingthe central axis L-L, surfaces 19c. [9e meet at a point. Additionally,the core lifter is longitudinally split at 29 so as to permit it toassume a shape of a smaller diameter or a larger diameter depending onwhether it is moved in the core lifter case and relative thereto in anouter direction or an inner direction.

The core lifter has a plurality of equally circumferentially spaced,axially elongated slots 30 that open to the outer edge 1%. The axialedge portions 30a, 30b of each slot 30 are parallel to one another andto a diameter of the core lifter while the axial inner edge portion 30cthat extends between edge portions 30a, 30b is located more thantwo-thirds of the axial distance from edge 19b to edge 19d. The corelifter also has a plurality of equally circumferentially spaced (otherthan for the two most closely circumferentially adjacent slot 29),axially elongated slots 31 that open to the inner edge 19d. The axialedge portions 31a, 31b of each slot 31 are also parallel to one anotherand to a diameter of the core lifter case while the axial inner edgeportion 310 that extends between edge portions 31a, 31b is located morethan two-thirds of the axial distance from edge 19d to edge 19b. In anyplane perpendicular to the core lifter axis that passes through bothsets of slots 30, 31 circumferentially spacing of one slot 31 from thead jacent slot 30 on each side thereof is substantially equal.Advantageously the two slots 30 that are circumferentially on eitherside of slot 29 are equally spaced therefrom.

The general radius of curvature R of the cylindrical inner surface 19 ofthe core lifter, when the core lifter abuts against edge a, or abutsagainst a stop ring (not shown) if such is provided in recess 20 asdisclosed in US. Pat. No. 3,340,939, is substantially the same as theinner radius of inner tube surface 17 a.

The structure of the apparatus of this invention having been described,the use thereof will now be set forth. For purposes of facilitatingdescription of operation of the apparatus of this invention, it will beassumed that the drill stem is extended into a hole in an earthformation in a generally downward direction even though the use of theinvention is not limited to drilling in a downward direction, and a corebarrel inner tube assembly is located in the drill stem in a position toreceive core as it is being drilled. Normally, at this time, the corelifter case is a substantial distance axially inwardly of recess 20 suchas illustrated in FIG. 1. Now the drill stem is moved axially inwardlyto have the core bit face 13b abut against the annular groove in theearth formation and the core drilling operation is started whereby thecutting of core is begun. Because of the annular shape of the core bit,an ever deepening hole is cut with a rod like core being produced. Asthe drilling continues, the drill stem, including the core bit, moverelative to the core whereby the core extends through the core bitaperture and thence into the core lifter case to abut against theadjacent surface of the core lifter. As the axial length of the coreincreases, the core lifter case moves relative the core lifter until thecore lifter abuts against the annular edge 17b of the inner tube (if nostop ring is provided, or ifa stop ring is provided in recess 20 againstthe stop ring). Thereafter, the core lifter case, the core lifter andthe core receiving tube together move axially as a unit relative thecore. In this connection, it is to be mentioned that in bothconventional core drilling apparatus particularly of the type for deephole drilling, a core barrel inner tube assembly is connected to aswivel so that the rotary motion of the drill stem is not imparted tothe core barrel inner tube but rather the inner tube and core liftercase usually only move axially relative the core as the drill stem isrotated.

After core of desired length has been cut, for example, when a highpressure signal is provided at the surface through conventionalstructure, the drilling is stopped and the drill stem is pulledoutwardly a short distance. Pulling the drill stem outwardly results inthe drill stem moving axially outwardly relative the core lifter caseuntil surface 12a abuts against surface l8b, provided appropriateconventional type of core drilling apparatus is used whereby the corelifter case is normally retained out of contact with the core bit.Assuming the core lifter case is movable relative the drill stem in theabove manner, after surfaces 12a, 18b are in abutting relationship,

further axially outward movement of the drill stem results in the corelifter case moving axially relative the core and the core lifter wherebythrough the drag of the core lifter on the core, the core lifter 19 isfurther axially spaced from groove 20 and is transversely compressed(due to tapered surfaces 23, I) to grippingly hold the core and breakthe core. After the core has been broken. either the core barrel innertube assembly is retracted relative the drill stem, or both the drillstern and core barrel inner tube assembly are retracted, depending uponthe type of core drilling apparatus being used.

As an example ofone embodiment of the invention, but not otherwise as alimitation in the invention, the following dimensions are given. Theoutside diameter for surface 1% at edge 19b is approximately 1.58inches, and at edge 1911 is approximately [.49 inches. The insidediameter for surface 19a is approximately l.42 inches. The length X ofthe core lifter as measured along axis L-L is one inch while thecorresponding length of surface 196 is three sixty-fourths of an inch.The spacing W of the most adjacent portion of edge portion 300 from edge1941 is approximately .250 inch while the spacing Z of the most adjacentportion of edge portion 31c from edge 19b is approximately .187 inch.The circumferential dimension C between each of edge portions 30a and30b, and edge portions 31a and 31b, for each of the respective slots is,in a core lifter relaxed condition, approximately .094 inch. Thecircumferentially spacing of the edges defining slot 29 in a core lifterrelaxed condition is approximately .l25 inch.

lclaim:

1. For an axially elongated core receiving tube, core lifter apparatuscomprising a core lifter case connected to one axial end of said corereceiving tube to extend axially away therefrom, said core lifter casehaving a radially outer surface, a gradually tapered radially innersurface portion that diverges in a direction toward said core receivingtube, said outer surface and tapered inner surface portion each having acentral axis, and a radially expandable core lifter mounted in said casefor limited slidable movement between a position remote from said tubeand a position more closely adjacent said tube, said core lifter havingan exterior tapered surface portion that forms a close fit with saidinner surface portion, a generally annular first edge that is axiallyadjacent the core receiving tube and an axially opposite edge,characterized in that said V core lifter has a first plurality ofaxially elongated circumferentially spaced slots opening to saidopposite edge that extends axially to terminate intermediate'said edges.

2. The apparatus of claim 1 further characterized in that said slotsextend more than two-thirds of the distance from said opposite edge tosaid annular edge.

3. The apparatus of claim 1 further characterized in that said corelifter has a second plurality of axially elongated, circumferentiallyspaced slots opening to said first annularedge and terminating axiallyintermediate said edges.

4. The apparatus of claim 3 further characterized in that each of thesecond slots is circumferentially offset from the first slots.

5. The apparatus of claim 3 further characterized in that each slot is.of an axial length that is substantially greater than one-halfoftheaxial length ofthe core lifter.

6. The apparatus of claim 5 further characterized in that the corelifter exterior surface is of a constant taper from the first annularedge to the opposite edge and that the core lifter has a cylindricaltransverse inner surface that extends axially from the first annularedge to axially adjacent the opposite edge.

7. For an axially elongated core receiving tube, core lifter apparatuscomprising an axially core lifter case having an end portion connectableto one end of said tube, a radially outer surface and a transverse innerconical surface portion of a gradual taper of progressively increasingtransverse dimension in an axial direction toward said end portion and acore lifter mounted in said core lifter case for limited axial movement,said core lifter having a transverse outer conical surface portion of ataper opposite the taper of the core lifter case, a generallycylindrical inner surface that is of a smooth continuous curvature forat least a major portion of the axial length of the core lifter, a firstannular edge. an opposite second annular edge, and a plurality ofcircumferentially spaced. axially elongated slots opening to the firstannular edge.

8. The apparatus of claim 7 further characterized in that said corelifter has a second plurality of circumferentially spaced, axiallyelongated slots opening to the second annular edge.

9. The apparatus of claim 8 further characterized in that each of saidslots is of an axial length that is more than onehalf the axial lengthof the core lifter.

10. The apparatus of claim 8 further characterized in that saidcorelitter is an axially split steel ring.

11. The apparatus of claim 8 further characterized in that the corelifter has a central axis and that the core lifter interior surface hasa substantially constant radius curvature throughout substantially itsentire axial length.

12. The apparatus of claim 8 further characterized in that said corelifter case end portion is threaded and that the core lifter has atleast six slots.

